The Apollo 17 crew caught this breathtaking view of our home planet as they were traveling to the moon on Dec. 7, 1972. NASA hide caption
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Science can sometimes come across as a stuffy, inflexible collection of facts — absolute truths not to be questioned. At least, that’s the way it is often taught in schools.
The reality of science is very different. Scientists are always questioning, holding out the possibility of being wrong, and learning new things by making mistakes. The progress of science is one long sequence if trials and errors — mostly errors.
But emphasizing the tentative, always-subject-to-revision nature of science can be taken too far. Science has taught us some things, after all. The computer on which you’re reading this really is made of atoms; future discoveries aren’t going to reveal that the very idea of atoms was just some kind of mistake. Scientific knowledge never reaches metaphysical certainty, beyond the pale of any possible revision; but there’s a lot we know with sufficient confidence that it’s not worth spending too much time in doubt.
Remarkably, the scope of what we do know is actually quite broad. In particular, it includes the basic particles and interactions that are responsible for absolutely everything that happens in a typical person’s everyday life. (Presuming that typical people don’t build dark-matter detectors or spend weekends jumping into black holes.)
Essentially everything you see around you as you go through your day is made of just three particles of matter — protons, neutrons and electrons — interacting through a handful of forces — gravity, electromagnetism and the nuclear forces. Together they make up the Core Theory, which has been tested experimentally in countless ways to exquisite precision. The fact that these particles and these forces are all we need to account for ourselves and our environments is as firmly established as the existence of atoms, and similarly unlikely to be overturned at any future time.
How can we be so sure? After all, there is unquestionably much we don’t know, from the ingredients of the dark cosmos to what happened at the Big Bang. And scientists through history have an embarrassing track record of proclaiming that we are very close to Having It All Figured Out, only to be proved wildly wrong when the next revolution came along.
But we’re not claiming to have it all figured out, or anywhere close. We claim to Have Some Things Figured Out. Those things just happen to include everything you and I are made of.
The reason we can be confident that we haven’t missed an important new particle or force that might be relevant to everyday life stems from the power of the basic framework of modern physics, quantum field theory (QFT). According to QFT, you can’t just toss in random new particles in any old way. If there were any new particles or interactions that could possibly play a role in everyday processes, then we could very easily make them or detect their existence, in particle accelerators or searches for new long-range forces. We’ve looked, hopefully and enthusiastically; they aren’t there.
It’s natural to imagine that QFT itself is wrong at some fundamental level. That’s certainly possible – anything’s possible. But QFT is extraordinarily robust. If you want to invent a theory that is compatible with the basic requirements of quantum mechanics, relativity and locality (events far away don’t affect what happens here), your theory is guaranteed to look like quantum field theory at the low energies characteristic of our everyday lives.
Indeed, QFT is almost certainly not the final word on physics at its most fundamental level. Spacetime itself might be emergent, for example, perhaps out of some tangle of loops or superstrings. But that won’t matter. Just as learning that air is made from molecules of nitrogen and oxygen and other atoms doesn’t change the fact that air is a gas with various properties (pressure, temperature, speed of sound), discovering the quantum reality underlying spacetime won’t change the effectiveness of quantum field theory in the everyday regime. Reality at its deepest level could be something utterly different than we have ever imagined, but we still have a good handle on how it behaves in front of our noses.
That knowledge has implications. You can’t bend spoons with your mind, and the location of Venus in the sky doesn’t affect your love life; there’s no way an unknown force can reach that far without us having detected it yet. More profoundly, there’s no way for our consciousness to survive after death; there’s simply no process by which the information in our brains can be preserved once our bodies shut down and decay.
As much as people love the excitement of discovery, we also have a soft spot for the romance of mystery. JJ Abrams has made wonderfully compelling movies and TV shows by exploiting the idea of a Mystery Box — a secret at the heart of a story that may or may not ever be revealed. It works well as a dramatic device, but when apprehending reality it’s important to acknowledge what we have learned, and accept the consequences of that hard-won understanding.
It’s easy, and wrong, to think of scientific truths as fixed and absolute. It’s also easy, and just as wrong, to act as if we know nothing and everything is up for grabs. We have a responsibility to do the hard work of figuring out exactly where the dividing line between knowledge and uncertainty lies, and take seriously what we do know.
Sean Carroll is a physicist at Caltech and author of The Big Picture: On the Origins of Life, Meaning, and the Universe Itself. Follow him at @seanmcarroll.
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